Recipe for a DIY composting toilet

2 wheelie bins, pickle barrels or plastic drums. I found two wheelie bins on the street in hard rubbish, and no I didn’t just steal people’s bins, they had cracks in them and a notice saying please take the bin. You need two because when one is full and the material is composting, you need another one to be adding to.

Milk crate, bakery tray and a piece of screen or plastic mesh (or anything you can find that will serve the same purpose). This is to make a raised platform in the base of the bin so that liquids can drain through, so the compost pile isn’t wet and smelly.

A piece of plastic plumbing (technical name) to attach a hose to the hole drilled at the base of the bin. I used a tap from a broken brew kit in hard rubbish.

Hose to drain liquid waste from the bin.

Two pieces of irrigation pipe.

Silicon sealant

Small amount of gravel

Bucket with lid – if you want to have an indoor toilet and empty the bucket about once a week. This doesn’t smell or attract flies at all if the shit is kept covered with organic matter and the lid is on when it’s not in use.

Toilet seat

Coarse organic material to add carbon and aeration to the composting system. This could be wood shavings, dry grass clippings, autumn leaves, shredded paper, rose petals, compost or whatever else is available. A friend was using lavender flowers for a while.

Utensils:

Hacksaw, drill

Method:

Cut the milk crate and bakery tray with a hacksaw to make a raised platform about 5cm above the base of the bin. Alternatively place bricks in the base and lay the tray on top. cover with screen or mesh to prevent solids falling through the platform.

Cut the irrigation pipe to a length to fit diagonally inside the bin. Drill small holes along the length of the pipe, plenty of them. This is to allow air to flow through the pile as it is composting, to prevent it from putrefying (no-one wants that, it would be stinky).

Drill a hole in the side of the bin, as close to the base as possible. This is for liquids to be drained out.

Attach a tap or plumbing bit into the hole. There are bits available for this purpose, that seal in place with plastic washers. Otherwise use silicon sealant to prevent leaks.

Attach the hose to the tap, and bury the other end of the hose in the ground, surrounded by gravel, so that the liquids can drain. This should be away from where vegetables are growing. This liquid contains pathogens so should not be left on the soil surface. If urine is kept separate most of the time the amount of liquid should be minimal.

Place a layer of bulking matter in the bin, small twigs or straw or something airy, and you’re ready to go!

You have a few options for the next bit. You could build an outhouse around the bin, or put it in a shed or outdoor laundry with a squatting platform, and deposit directly into it.

Otherwise you could put a bucket in your bathroom and build a commode around it, or place a toilet seat directly on the bucket. Some go even more low tech and simply squat over the bucket.

Add a handful of carbon material every time you go, enough to cover it.

When a bin is full, leave it to break down for 6months to a year, and then bury the compost under the ground. It may still contain pathogens so it’s best not to leave it on the soil surface. Adding compost worms can help with the composting process. Unlike most people, they like nothing better than living in a pile of shit. They tend to die during heatwaves though.

Urine can go directly on the garden. it is great fertiliser for the garden, it is high in nitrogen and contains all the nutrients that plants need. By peeing in a flush toilet, we are not only wasting water, but a valuable resource.

Urine is sterile, so is not introducing any pathogens to the garden, and unless it is concentrated in one place, doesn’t create any smells. Diluting it in water is recommended, as the high nitrogen content can damage plant roots.

Scientist James Lovelock hypothesises that urine is a result of a symbiotic evolution with plants, as we actually expend otherwise unnecessary energy to expel our wastes in a form that is readily available to them.